Large shells manufacturing apparatus

ABSTRACT

An apparatus for additive manufacturing of large 3D hollow objects with thin walls, includes a 3D hollow object material deposition module configured to deposit a portion of material forming at least a layer of a 3D hollow object wall; a 3D hollow object material solidifying module configured to solidify at least the portion of material forming at least a layer of the 3D hollow object wall; and a support material dispensing module configured to dispense a support material across a cross section of the 3D hollow object wall. The support material is dispensed separately prior to or concurrently with the deposition of the portion of material forming at least a layer of a 3D hollow object wall.

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 14/265,586 filed on Apr. 30, 2014.

The apparatus and method relate to additive manufacture apparatuses andin particular to manufacture of physical objects such as large shells.

BACKGROUND

Manufacture of three dimensional (3D) models or objects is an additivemanufacturing process by means of which a computer generated 3D model isconverted into a physical object. The process, sometimes termedstereo-lithography, involves generation of a plurality of materiallayers of different or identical shapes that are laid down or depositedon top (or bottom) of each of the preceding layer until the amount oflayers results in a desired physical object.

The material from which the layers of the physical object are generatedcould come in liquid, paste, powder, gel and other aggregate state. Thematerials are dispensed by a plurality of methods including inkjetprinting, extrusion and sintering. Conversion of such materials into asolid form is typically performed by suitable actinic radiation and/orheat.

Manufacturing of 3D models and objects spans over a large range ofapplications. This includes prototype manufacture, small runs ofdifferent products manufacture, decorations, sculptures, architecturalmodels, and other physical objects.

Recently, manufacture of relatively large size physical objects andmodels has become popular. Large size statues, animal figures, signageletter, and decorations are manufactured and used in differentcarnivals, playgrounds, and supermarkets. Where the manufacturingtechnology allows, some of these physical objects are manufactured as asingle piece at 1:1 scale and some are coming in parts assembled intothe physical object at the installation site. Manufacturing of suchlarge objects consumes significant amount of relatively expensivematerials and techniques to reduce the amount of the expensive materialsby including in the manufactured object different support orreinforcement structures have been developed. Methods for manufacture ofsuch supports or reinforcement structures are described for example, inU.S. Pat. Nos. 5,595,703; 6,797,351; 8,285,411; and US PatentApplication Publication 2010/0042241.

Introduction of support or reinforcement structures allows small savingson material costs since some of the objects are manufactured as shellsor hollow structures. However, large shells could warp, or otherwisedeform even in course of their manufacture and multiple supportstructures integral with the shells or constructed at the installationsites are required. Since the objects manufactured as shells have theirinner space hollow or empty, the support structures are mounted ormanufactured to be located in these hollow spaces. Although for someshells, the support structures located in the hollow inner space are notsufficient and frequently they become augmented with outer supportstructure that in addition to cost adversely affect the visualappearance of the object. These support structures significantlyincrease the object production time, consume costly material, andrequire additional labor to install them and to remove some of theunnecessary material.

GLOSSARY

“Shell”—as used in the current disclosure the term shell means astructure or a physical object, usually hollow inside, the wallthickness of which is small compared to its other dimensions. The shellstructure could be a curved structure with a curvature of second orhigher power; although in some examples it could have certain flatnessor flat segments.

“Curvature”—as used in the current disclosure the term curvature is theamount by which a geometric object deviates from being flat, or straightin the case of a line.

“Curvature change ratio”—as used in the current disclosure the termcurvature change ratio means the ratio of the change in the angle orslope of a line tangent that moves over a given segment of a curve orarc. First derivative defines a slope of the line tangent to the curve.

“3D physical object shell material” or “shell material”—as used in thecurrent disclosure means the material from which the shell ismanufactured.

“Support material” and “grid”—as used interchangeably in the currentdisclosure the term support material means material from which the shellmaterial support is made.

“Frequency of support material dispensing”—as used in the currentdisclosure the term frequency of support material dispensing means thefrequency of support material dispensing as a function of the curvaturechange ratio.

“Aspect ratio”—as used in the current disclosure the term aspect ratiomeans a ratio of the height of the generated feature to the thickness ofthe generated feature.

“Horizontal plane”—as used in the current disclosure horizontal planemeans a plane normal to the gravitational force. Vertical plane is aplane perpendicular to the horizontal plane.

“Conventional support”—as used in the current disclosure the termconventional support means support structures known at least from thereferences listed.

The terms “3D hollow object” and “shell” are used interchangeably in thecurrent disclosure and have the same meaning.

SUMMARY

Disclosed is an apparatus for additive manufacturing of large 3D hollowobjects, also termed shells. Such objects typically have thin walls. Theapparatus includes a 3D hollow object material deposition moduleconfigured to deposit a portion of material forming at least a layer ofa 3D object shell wall, a 3D object material solidifying moduleconfigured to solidify at least the portion of material forming thelayer of the 3D object shell wall; and a support material dispensingmodule configured to dispense a support material across a cross sectionof the 3D object.

The 3D hollow object material deposition module of the apparatus couldbe an inkjet module, an extrusion module, a material sintering module,or any other known material deposition module. The 3D hollow objectmaterial solidifying module could be a module configured to provideultraviolet radiation, infrared radiation, microwave radiation, andheat.

The support material is dispensed across the cross section of the 3Dhollow object as a function of at least one of 3D hollow object or shellwall characteristics. The characteristics could include the angle of the3D hollow object wall with a horizontal surface or wall curvature changeratio. The support material could be one of a group of materialsconsisting of a metal grid, a plastic grid, a fabric grid, a grid madeof material dissolvable in material of which the 3D hollow object ismade or made of the same material of which the 3D object is made, and acombination of all of the above. Upon completion of the 3D hollow objectmanufacture, the support material becomes embedded into the 3D hollowobject material.

The support material dispensing module dispenses the support materialmore frequent at segments of the 3D hollow object walls with flat andtilted surface that are at large tilt angles with respect to horizontalsurfaces. For curved walls the frequency of the support materialdispensing is a function of curvature change ratio or the angle of thetangent to the curved surface with the horizontal surface, for example,the support material dispensing module dispenses the support materialmore frequent at segments of the 3D hollow object proximate to the curvemaxima, minima or inflection points or at segments with large anglesbetween the tangent to the curved surface with the horizontal surface.

The method of manufacture of 3D hollow objects or shells supports acombined support material dispensing process with use of conventionalsupport structures of 3D hollow object or shell. Conventional typesupport structures could be implemented concurrently with introductionof a more rigid support material, for example, a metal grid or net couldbe dispensed instead of a plastic grid. Support material could bedispensed across the whole cross section of the shell including over thehollow spaces to become included in the conventional support structures.This resin reinforces the conventional support structures that now couldconsume essentially less of expensive 3D object material than supportstructures without support material would consume. Conventional supportscould be introduced at a different frequency or distance between them.The curvature change ratio or the angle of the tangent to the curvedsurface or flat segments or the shell with the horizontal surfaces woulddefine the frequency of conventional support structures. Theconventional support structures could be perpendicular to the supportmaterial layers or at an angle to the support material or the 3D hollowobject or shell. Different types of conventional supports could be usedin a combination with different support materials.

The apparatus for and method of manufacture also support manufacture of3D hollow objects or shells having appendages obviating the need forexternal support or construction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an apparatus for additivemanufacturing of large 3D hollow objects or shells, according to anexample;

FIGS. 2A-2C are schematic illustrations of a large 3D hollow objectorshell, according to an example;

FIGS. 3A-3B are schematic illustrations of a stage in a large 3D hollowobject or shell manufacturing according to an example. The figureillustrates shell material deposition process including support materialdispensing process;

FIGS. 4A-4B are schematic illustrations of a next stage in a large 3Dhollow object or shell manufacturing process according to an example.The figure illustrates shell material deposition process includingsupport material dispensing process;

FIGS. 5A-5B are schematic illustrations of a further stage in a large 3Dhollow object or shell manufacturing process according to an example.The figure illustrates shell material deposition process includingsupport material dispensing process;

FIG. 6 is a schematic illustration of a support material dispensingprocess for an apparatus for additive manufacturing of large 3D hollowobjects or shells, according to an example;

FIG. 7 is a schematic illustration of a combined support materialdispensing process with use of conventional support structures formanufacture of large 3D hollow objects or shells, according to anexample;

FIG. 8 is a schematic illustration of a combined support materialdispensing process with use of conventional support structures of large3D hollow objects or shells that include flat and curved wall segments;

FIGS. 9A and 9B, collectively referred to as FIG. 9 are schematicillustrations of final stages of manufacture of a large 3D hollowobjects or shells, according to an example;

FIGS. 10A, 10B, 10C, 10D, 10E, 10F, and 10G are schematic illustrationsof support material dispensing process for an apparatus for additivemanufacturing of large 3D hollow objects or shells, according to anotherexample;

FIG. 11 is a perspective view simplified illustration of an exemplarysolution common in the art for manufacturing large scale 3D objectshaving overhanging appendages; and

FIGS. 12A, 12B, 12C, 12D, 12E and 12F, together referred to as FIG. 12,are perspective view and plan view simplified illustrations ofimplementation of a support material grid in construction of a 3D objecthaving appendages.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In some of the manufacturing applications, where large size 3D objectsor models are produced by additive manufacturing processes, the externalappearance or segments of the object exposed to an observer is moreimportant than the inner segments or volumes of the 3D hollow object orshell. Such 3D objects are usually manufactured by producing relativelythin shells of for example, shells with walls having 1 mm to 5 mm oreven 8 mm thickness. The size of the manufactured 3D object could besignificant for example, between 100 mm by 100 mm; 1000 mm by 1000 mm oreven 10000 mm by 10000 mm. In addition, the 3D object could includesubstantial segments with curved surfaces and walls. At certain size ofthe wall segment, the wall segment tilt and curvature change ratio theshell walls could become not stable and even collapse. Currently, toavoid collapse of the flat tilted and horizontal walls as well as curvedwalls, such 3D objects or models are manufactured by providing numeroussupports structures made of the same material as the 3D object is made.The support structures are typically located in the inner segments ofthe 3D object. Such support structures are not visible to the observerand do not affect visual perception of the 3D object.

Currently, all systems manufacturing 3D objects operate in rasterscanning mode. These support structures significantly increase the 3Dhollow object production time, consume costly material, increases final3D object weight and require additional labor to remove some of theunnecessary material. In some instances, the inner space of such objectscould be filled in with porous material. This reduces the weight of the3D object, but requires significant, typically manual, procedures.

The current document discloses an apparatus and method that supportmanufacture of large 3D hollow objects or shells with thin wallsincluding curved walls and surfaces with high and low curvature changeratio and alleviate or significantly reduce the need for supportstructures. Further to this, introduction of support structures becomesa function of the curved wall segment curvature change ratio or theangle between a flat wall and a horizontal surface.

Reference is made to FIG. 1 which is a schematic illustration of anapparatus for additive manufacturing of 3D objects such as hollowobjects with thin walls or shells, according to an example. Apparatus100 includes a 3D hollow object or shell material deposition module 104configured to deposit a portion of material forming a segment or a layer216 (FIG. 2A) of a 3D hollow object 200 or shell wall 204, a 3D objectmaterial solidifying module 108 configured to solidify at least theportion of material deposited and forming a segment or a layer 216 ofthe 3D hollow object or shell 204, and a support material dispensingmodule 112 configured to dispense a support material across the crosssection of the 3D hollow object. Support material dispensing module 112dispenses the support material, which could be a plastic grid, a metalgrid or fabric net and a grid made of the same material of which the 3Dobject is made across the whole cross section of the 3D hollow objectincluding over the hollow spaces of the 3D object or shell. Supportmaterial dispensing module 112 could be configured to dispense a numberof different support materials. Alternatively, apparatus 100 couldinclude a number of support material dispensing modules 112-1, 112-2 andso on, with each module configured to dispense different supportmaterial. The support material dispensing module 112 could also includea stretching mechanism 114 configured if necessary to stretch andtension each dispensed support material layer to provide the desiredlevel of tension and stability to the 3D object or shell.

Apparatus 100 could also include a computer 128 configured to receivethe 3D hollow object design information from a CAD system, adapt the 3Dhollow object design information to a particular manufacturing process,and control the apparatus for additive manufacturing of 3D hollowobjects or shells.

The 3D hollow object 200 and in particular shell 204 (FIGS. 2A-2C) ofthe 3D hollow object could be manufactured by employing materialdeposition module 104 to deposit a plurality of 3D object materiallayers of different or identical shape. The layers are laid down ordeposited on top (or bottom) of each of the preceding layer until theamount of layers results in a desired 3D object. In one example, the 3Dobject to be manufactured could be located on a support or table 116configured to move in three directions. The direction could be the knowX, Y, and Z axes. Alternatively, instead of moving support table 116 inthe three directions, material deposition module 104 could be configuredto move in the three directions over the support table 116. In anotherexample, the movement in the three directions could be split between thesupport table 116 and material deposition module 104.

The 3D physical object material deposition module 104 could employalmost any know material deposition technology. It could be an inkjetmodule 120, a material extrusion module 124, a material sinteringmodule, and other modules as well as a combination of different materialdeposition modules. Further to this, each material deposition module 104could include a plurality of ink ejecting printheads, a plurality ofmaterial extrusion nozzles, and a combination of the above.Additionally, the plurality of ink ejecting printheads or the pluralityof material extrusion nozzles could be configured to supportsimultaneous manufacturing of different segments of the 3D hollowobject. The plurality of ink ejecting printheads or the plurality ofmaterial extrusion nozzles could also be configured to deposit differentmaterials and materials of different color.

The existing 3D manufacturing systems produce 3D objects and shells withtheir support structures in raster scanning format. Such type ofscanning results in long manufacturing times. The present system couldform a 3D hollow object or shell 204 in a vector type of movement,significantly reducing the manufacturing time. In some examples, supporttable 116 with located on it 3D hollow object 200 could be configured torotate as shown by arrows 212 around an axis 220 (FIG. 2), which couldbe the Z axis or central axis of the support including rotation about anoffset axis when the support is moved in X or Y direction. However, asit will be shown below it is more convenient and simple to move thesolidification radiation source or a scanning laser beam.

As shown in FIG. 2A, apparatus 100 forms 3D hollow object 200 or onlythe shell 204 by depositing a plurality of 3D physical object materiallayers 216. The layers could be of different or identical shape and theyare laid down or deposited on top or bottom of each of the precedinglayer until the amount of layers results in a desired 3D hollow object.The material from which the layers of the 3D hollow object are laid downcould come in liquid, paste, powder, gel and other aggregate state. Thematerial from which the layers 216 of the 3D hollow object 200 are laiddown also could come in a plurality of colors. The colors could becolors such as Gray, Orange, Blue, White, Green, Black, and others.Thick line 210 schematically illustrates the thickness of the object 200wall.

As it was disclosed above the material from which the layers of the 3Dhollow object are laid down could come in a variety of aggregate states.Physical object material solidifying module 108 is configured tosolidify or convert these materials into a solid aggregate state. Thesolidifying module 108 (FIG. 1) typically solidifies the 3D hollowobject material layers 212 by material solidifying radiation or simplyradiation. In some examples, the 3D hollow object material could includedeposition of a number of different materials that solidify by achemical reaction between them, for example, epoxy like materials. Theradiation could be an ultraviolet radiation, infrared radiation, laserradiation, microwave radiation, and heat. Material solidifying module108 could include a source of radiation emitting one type of radiationor a number of radiation sources emitting different types of 3D objectmaterial solidifying radiation.

The 3D object material solidifying radiation could be applied in a floodradiation mode where all of the 3D object material isilluminated/irradiated and solidified, or through a digital mask such asa DLP® modulator or switch commercially available from TexasInstruments, Inc., Dallas Tex. 75201 U.S.A., or in a laser scanningmode. The digital mask (DLP) and laser scanning mode of solidifyingradiation application support selective solidification of desiredsegments of a deposited 3D hollow object material.

Regardless of how and where the successive layers 212 of 3D hollowobject material are laid down on a the top or bottom of the previouslayer, when the aspect ratio of the manufactured shell with flatvertical or horizontal walls reaches certain proportions the shell tendsto collapse. It was experimentally determined that dependent on the typeof material deposited, at aspect ratio of 1:10 to 1:100, the shellbecomes not stable and as the material deposition continues, the shelltends to collapse. According to an example, the support materialdispensing module 112 (FIG. 1) dispenses a support material across across section of the 3D hollow object or shell, including hollow spaces,when the 3D object shell vertical walls aspect ratio exceeds at least1:15 or 1:20. Depending on the aspect ratio of the 3D hollow objectwalls, material of the walls, cost considerations, and other parameterscomputer 128 could be configured to adapt operation of support materialdispensing module 112 to operate at different aspect ratios, for exampleat 1:15 or 1:50 or even 1:5. Computer 128 could also be configured, asit will be explained below, to adapt operation of support materialdispensing module 112 to dispense support material at differentfrequency or a different support material a function of the shell wallangle with the horizontal plane. The support material could be suchmaterial as a metal grid, a plastic grid, a fabric grid, a grid made ofmaterial dissolvable in the 3D physical object material, and acombination of all of the above.

FIGS. 3A-3B are schematic illustrations of a stage in a large 3D hollowobject or shell manufacturing according to an example. The figureillustrates 3D hollow object material deposition process includingsupport material dispensing process. The support material dispensingmodule 112 (FIG. 1) dispenses periodically the support material 304(304-1) across a cross section 308 of the 3D hollow object 200 includingthe hollow or empty space 312. The support material could be one of agroup of materials consisting of a metal grid, a plastic grid, a fabricgrid, a grid made of material dissolvable in the 3D hollow objectmaterial, and a combination of all of the above.

According to one example, the period between two successive supportmaterial dispenses is generally determined by the time required todeposit a portion of material sufficient to generate a stable segment ofa 3D hollow object or shell. The period or frequency of support materialdispensing could be set depending on the angle of the walls (tilt) witha horizontal surface, or the curvature change ratio, or on the aspectratio of which exceeds for example, 1:10 or 1:50 or any other ratiodictated by the material used and other listed above parameters. In someexamples, the frequency of support material dispensing could be setaccording to the requirements of the most critical wall to bemanufactured, which could be a curved or tilted wall.

FIGS. 4A-4B and FIGS. 5A-5B illustrate progressive stages in themanufacture of a large 3D hollow object or shell material depositionprocess including support material dispensing process. FIGS. 4A-4Billustrate the next stage in a large 3D hollow object or shell material216 deposition process, where following deposition of a number of 3Dhollow object or shell material layers 216 a layer of support material304 (304-1, 304-2; 304-3) is dispensed. The process continues until themanufacture of the 3D physical object shell is completed. The type andsize of the support material 304 could be adapted to the particularcross section size and strength.

According to another example the support material dispensing module 112dispenses periodically the support material across a cross section ofthe 3D hollow object and the period between two successive supportmaterial dispenses is generally a function of the 3D hollow object shellcurvature. The shell curvature is typically a second or higher powercurvature. It could have curvature maxima and minima points as well ascurvature inflection point or points. The support material dispensingmodule 112 at these points would dispense the support material at ahigher frequency than at other segments of the shell. Upon completion ofthe shell or 3D hollow object manufacture, the excessive supportmaterial could be trimmed at least at the external surfaces of theshell. Support material 304 can also be dispensed separately and appliedmid-dispensing of the final 3D object as will be explained in greaterdetail below.

FIG. 6 is a schematic illustration of a support material dispensingprocess for an apparatus for additive manufacturing of a 3D hollowobject or shell, according to an example. Shell 600, is half of anellipsoid. Deposition process of shell material 216 is similar to theones described above. Following deposition of a number of 3D physicalobject or shell 600 material 216 a layer of support material 304 isdispensed. Support material 304 could be a metal grid, a plastic grid ora grid made from the same material or resin of which the 3D object ismade. The frequency of the support material 304 dispensing increases(inversely proportional) as a function of the angle 608 between the 3Dobject shell and horizontal plane 612 or plane defined by X-Y axes. Thelarger the angle 608 becomes the more frequent support material 304 isdispensed. The stretching mechanism 114 of support material dispensingmodule 112 could also be configured to stretch and tension eachdispensed support material layer to provide the desired level of tensionand stability to the 3D object or shell.

According to one example, concurrently with the increase of the supportmaterial 304 dispensing frequency, support material 304, could bereplaced by a more rigid support material, for example, a metal grid 604could be dispensed instead of a plastic grid 304 or plastic or resingrid of different strength and mesh could be dispensed. Support material304 can also replaced by a separately dispensed support or grid 920(FIG. 10) and applied mid-dispensing of the final 3D object as will beexplained in greater detail below. As it was indicated above, supportmaterial dispensing module 112 could be configured to dispense a numberof different support materials. Alternatively, apparatus 100 (FIG. 1)could include a number of support material dispensing modules, with eachmodule configured to dispense different support material.

According to one example, and in particular at large angles 608 betweenthe 3D object shell and horizontal plane 612 or plane defined by X-Yaxes, support material 304 dispensing frequency could be increased, thelevel of support material stretching could be changed, or introductionof a more robust support material 604 replacing support material 304could be implemented. According to another example, and in particular atlarge angles 608 between the 3D object shell and horizontal plane 612 orplane defined by X-Y axes, concurrently with the use of support material304 or 604, a plurality of conventional support structures 704 (FIG. 7)could be implemented. FIG. 7 is a schematic illustration of a combinedsupport material dispensing process with use of conventional supportstructures for manufacture of large 3D hollow objects or shells,according to an example. Conventional type support structures 704 couldbe implemented concurrently with introduction of a more rigid supportmaterial, for example, a metal grid 604 could be dispensed instead of aplastic grid 304. In addition the level of support material stretchingcould be varied. Properly dispensed and stretched support materialprovides a sufficient support basis for additional conventional supportstructures. Since the support material could be dispensed to becomeincluded or embedded in the conventional support structures 704 itenforces the conventional support structures 704. Reinforcedconventional support structures 704 could consume essentially less ofexpensive 3D hollow object material than support structures withoutsupport material would consume. Upon completion of the shell or 3Dhollow object manufacture, the excessive support material 304 or 604could be trimmed at least at the external surfaces of the shell.

When 3D hollow object walls are at an angle (tilted) to a horizontalsurface, the weight of the wall under influence of gravity could developa force sufficient to distort and even destroy the wall. Depending onthe angle at which a particular 3D hollow object wall is oriented to thehorizontal plane computer 128 (FIG. 1) could be configured to adaptoperation of support material dispensing module 112 to operate atdifferent frequency for manufacture of 3D hollow object walls as afunction of the wall angle 608 with the horizontal plane 612. For largeangles, for example, 50 degrees to 80 degrees, of the wall with thehorizontal plane, computer 128 could operate support material dispensingmodule 112 at a higher frequency or shorter time intervals than forlarge angles of the wall with the horizontal plane, for example 50 or 80degrees or more. In addition the level of support material stretchingcould be varied. For all practical purposes the frequency of supportmaterial dispensing could be adapted to include different wall anglesand thicknesses, wall size, wall materials, cost considerations andothers.

The conventional support structures could be perpendicular to the shellwalls or at an angle to the 3D hollow object or shell walls. Differenttypes of conventional supports could be used in a combination withdifferent support materials.

Usually, 3D hollow objects 200 and 800, as shown in FIGS. 2 and 8include a mix of plane and curved surfaces. Curved surfaces could becharacterized by a curvature change ratio parameter or the change in theangle or slope of a line 804 tangent that moves over a given segment ofthe curved surface. Similar to the disclosed above considerationscomputer 128 (FIG. 1) could be configured to operate the supportmaterial dispensing module 112 to dispense a support material across across section of the 3D hollow object or shell as a function ofcurvature change ratio.

Computer 128 (FIG. 1) could also be configured to operate the supportmaterial dispensing module 112 to dispense a support material across across section of the 3D hollow object or shell and account for suddenchanges in the weight to be supported. Such sudden changes in the weightcould be caused by a snow fall or a rain.

Computer 128 could also be configured to optimize the combination(hybrid) between conventional support 704 and dispensed support material304 or 604. The optimization could include the number of conventionalsupport structures as a function of shell wall angle or curvature changeratio, cost optimization, and 3D object shell stability. Conventionalsupports could be introduced to be perpendicular to the support materiallayers or at an angle to the support material or the 3D object shell.Different types of conventional supports could be used in a combinationwith support material 304 or 604.

Use of large signage and in particular letters is a one of theapplications that the present apparatus could simplify by reducing theamount of material used, reducing the manufacturing time and costs. FIG.9 is a schematic illustration of stages of manufacture of a large 3Dhollow object such as letter A according to the present method, althoughit is clear that any other letters or shells could be manufactured usingapparatus 100 and the manufacturing method described above.

FIG. 9 is a schematic illustration of final stages of manufacture of alarge 3D hollow object or shell, which in this particular case is alarge size letter A.

In FIG. 9A manufacture of the observable surface 928 of the letter “A”is accomplished and almost ready 3D letter “A” could be safely removedfrom support 116 of apparatus 100.

FIG. 9B illustrates a final stage in 3D hollow object (letter “A”)manufacturing process. Upon completion of the 3D hollow objectmanufacture, the excessive support material 920 could be trimmed atleast at the external surfaces of the object.

In another example depicted in FIGS. 10A, 10B, 10C, 10D, 10E, 10F and10G collectively referred to as FIG. 10, support material or grid 920can be made from the same material (resin) of which the 3D object itselfis made and dispensed separately. The separately dispensed support orgrid could be placed across a hollow volume of a cross section of the 3Dhollow object or shell at a predetermined level.

Grid 920 can be made of a single layer thickness or have a thicknessexceeding single layer thickness and include ribs 1012, shown in FIG.10D to be positioned so that to provide additional strength to grid 920as required.

An advantage of this technique is in that support material 920 can beintegrated into the walls 1016 of the three dimensional object as it isbeing manufactured without leaving any external appendages or excessivesupport material 920 that later require trimming or removal at least atthe external surfaces of the object or cannot be removed at all as willbe described in greater detail below. Another advantage of a separatelydispensed support or grid is in shortening the throughput time formanufacturing the 3D object by manufacturing support material 920separately prior to or concurrently with the manufacturing of the 3Dobject.

FIG. 10A, which is a perspective view simplified illustration of acomputer-generated model 1000 for a 3D object 1050 (FIGS. 10E-10G) to bemanufactured, depicts a planned wall 1016 of the planned 3D object 1050.Computer 128 (FIG. 1) could calculate one or more cross-section levelsat which positioning of one or more support material 920 grids wouldprovide 3D object 1050 with optimal structural strength and stability.

Generated model 1000 generated by computer 128 can also mark (emphasizedin FIG. 10A with thick phantom lines) the exact planned contour outlineof planned wall 1016 of 3D object 1050 to be manufactured at across-section level (l₁; l₂) at which support material 920 is to bepositioned as determined by computer 128 to provide optimal structuralstrength and stability. Such contour outlines are marked in FIG. 10A ascontour outline 1010 at a first level Op and a contour outline 1020 at asecond level (l₂) and define the precise borders of support material orgrid 920 to be dispensed.

Once the outline of the required support grid is determined by computer128, material dispensing module 112 (FIG. 1) or a separate materialdispensing module (not shown) can separately dispense support material920 the borders of which are precisely defined by outlines 1010 and 1020and which can be made from the same material (resin) from which the 3Dobject is made and at a location other than the location at which the 3Dhollow object is being dispensed.

Support material 920 can be dispensed across cross section contour 1010and across cross section contour 1020 of 3D object 1050 including acrossthe hollow or empty space 1014 inside contour 1010 and empty space 1024inside contour 1020 so that the borders of support material or grid 920fit precisely the planned contour outline in accordance with thegenerated model of 3D object 1050.

As discussed above, support material 920 or grid can be dispensedseparately in accordance with the desired planned contour outlines priorto or concurrently with the dispensing of 3D object 1050.

Additionally and optionally, support material 920 can be dispensed alonga contour outline such as border 1018 of contour 1010 in asemi-continuous fashion so that to form a non-continuous border such asthat depicted in FIG. 10B or, alternatively and optionally, a contouroutline such as border 1028 can be dispensed in the form of depositedthickened drops (exceeding thickness of a single layer) so that to formedge anchor bonding points 1030 (FIG. 10C) to be integrated into thelater dispensed wall of 3D object 1050. Dispensing support material orgrid 920 made from a material being the same or similar to that of whichthe 3D object is made can contribute to a smooth and simple integrationof the materials of support material or grid 920 and the 3D object.

Once the support material or grid 920 has been dispensed aspredetermined by computer 128, i.e., in form dictated by contours 1010and/or 1020, manufacturing of the 3D object can proceed. FIG. 10E, whichis a perspective view simplified illustration of a 3D object beingmanufactured, illustrates partially manufactured 3D object 1050 beingmanufactured according to computer-generated model 1000 (FIG. 10A) for a3D object.

In FIG. 10E support material 920 of contour 1010 has already beendispensed and placed at level (l₁). At this stage, the manufacturing of3D object 1050 has ceased at level (l₂) so that pre-dispensed supportmaterial 920 of contour 1020 can be placed over the cross-section of 3Dobject 1050 at level (l₂) as illustrated in FIG. 10E by an arrowdesignated reference numeral 1070.

As shown in FIG. 10F, which is a perspective view simplifiedillustration of a 3D object being manufactured, support material or grid920 of contour 1020 is in place and manufacturing of 3D object 1050 cancontinue. FIG. 10G shows a perspective view of the final product withsupport material 920 of contour 1010 (not shown) and support material920 of contour 1020 in place. It can be appreciated that upon completionof the 3D hollow object manufacture, support material 920 does notprotrude from at least the external surface of 3D object 1050 and henceno further trimming or any other treatment of 3D object 1050 at leastexternal surface is necessary. Another advantage of a separately,pre-dispensed support material or grid 920 is in that it can be employedas a hidden from the eye support for overhanging appendages of the 3Dobject to be manufactured.

FIG. 11, is a perspective view simplified illustration of an exemplarysolution common in the art for manufacturing large scale 3D objectshaving overhanging appendages. As shown in FIG. 11, which is a largescale head of a horse 1100, the front part 1102 of the horse's head maybe quite heavy and must be supported by a beam 1104 to prevent thebreakage at the nape of the neck 1106.

FIGS. 12A, 12B, 12C, 12D, 12E and 12F, together referred to as FIG. 12,are perspective view and plan view simplified illustrations ofimplementation of a support material grid in construction of a 3D objecthaving appendages.

FIG. 12A depicts a computer 128 generated 3D model 1200 and a plannedwall 1216 (FIGS. 12D-12F) of the planned 3D horse head 1250 to bemanufactured similar to the model 1000 of FIG. 10A. Computer 128(FIG. 1) could calculate one or more cross-section levels at whichpositioning of one or more support material 920 grids would provide 3Dobject 1250 with optimal structural strength and stability.

Once contour and position of one or more support material 920 grids isdetermined, computer 128 can also define one or more portions of 3Dobject 1250 to be manufactured on one or more surfaces of supportmaterial 920 one or more grids. In FIG. 12A, computer 128 has defined aportion 1202 according to which a first portion 1252 of 3D object 1250can be manufactured based on a first surface 922 (FIG. 12C) of supportmaterial 920 grid and a second portion 1204 according to which a secondportion 1254 of 3D object 1250 can be manufactured based on a secondsurface 924 (FIG. 12D) of support material 920 grid.

In one example grid 920 can have two or more surfaces each surfaceproviding can be flat and have a first surface 922 and a second surface924 wherein first surface 922 and second surface 924 are on oppositesides of the grid.

Generated model 1200 generated by computer 128 can also mark (emphasizedin FIG. 12A with thick phantom lines) the exact planned contour outlineof planned wall 1216 of 3D object 1250 to be manufactured at across-section level (l₃) at which support material 920 is to bepositioned as determined by computer 128 to provide optimal structuralstrength and stability. Such a contour outline is marked in FIG. 12A ascontour outline 1210 at a first level (l₃) and defines the preciseborders of support material or grid 920 to be dispensed. In FIG. 12A,contour 1210 is selected at a level at which a volume defined by thecontour at the selected level (l₃) has the largest area. However, thisis not necessarily a requirement and selected level (l₃) is notarbitrary and is determined by computer 128 to provide optimalstructural strength and stability of the 3D object to be manufactured.

As shown in FIG. 12B, once the outline of the required support grid isdetermined by computer 128, material dispensing module 112 (FIG. 1) or aseparate material dispensing module (not shown) can separately dispensesupport material 920 the borders of which are precisely defined byoutline 1210 and at a location other than the location at which the 3Dhollow object is being dispensed. Support material 920 can be made fromthe same material (resin) from which the 3D object is made. In FIG. 12B,support material or grid 920 can be made of a single layer thickness orhave a thickness exceeding single layer thickness and include ribs 1012,shown in FIG. 12B to be positioned so that to provide additionalstrength to grid 920 as required.

Support material 920 can be dispensed across cross section contour 1210of 3D object 1250 including across the hollow or empty space 1214 insidecontour 1210 so that the borders of support material or grid 920 fitprecisely the planned contour outline in accordance with the generatedmodel of 3D object 1250.

As discussed above, support material 920 or grid can be dispensedseparately in accordance with the desired planned contour outlines priorto or concurrently with the dispensing of 3D object 1250.

Support material or grid 920 of FIG. 12B is shown to be flat having twosurfaces 922 and 924 (FIGS. 12D and 12E) on opposite sides thereof.However, and as shown in FIG. 12C, support material or grid 920 can havemore than two surfaces laying in multiple planes in 3D space as requiredto provide optimal structural strength and stability of the 3D object tobe manufactured.

As illustrated in FIG. 12D, a first surface 922 of support material orgrid 920 can, initially, form a base support layer upon which a firstportion 1252 of 3D object 1250 can be dispensed. FIG. 12D, which is aperspective view simplified illustration of a 3D object beingmanufactured, illustrates the complete first portion 1252 of partiallymanufactured 3D object 1250 manufactured according to computer-generatedfirst portion 1202 of model 1200 (FIG. 12A) for a 3D object.

This point, incomplete 3D object 1250 can be inverted, as illustrated inFIG. 12E. Once inverted, second portion 1254 of 3D object 1250 can bedispensed on second surface 924 of support material or grid 920,completely burying support material or grid 920 inside 3D object 1250obviating the need for any external support such as a beam 1104 (FIG.11). Also in this example no further trimming or any other treatment of3D object 1250 at least external surface is necessary.

FIG. 12F illustrates the final 3D object with no external support orprotruding material. Support material or grid 920 is buried inside wall1216 as outlined by a phantom-line.

The apparatus and method described substantially reduce the time andcost of additive manufacture of the large 3D hollow objects. Acombination of conventional supports with support material improves thestrength of the 3D hollow objects and reduces their manufacturing cost.

What is claimed is:
 1. An apparatus for additive manufacturing of large3D hollow objects with thin walls, said apparatus comprising: a 3Dhollow object material deposition module configured to deposit a portionof material forming at least a layer of a 3D hollow object wall; a 3Dhollow object material solidifying module configured to solidify atleast the portion of material forming at least a layer of the 3D hollowobject wall; and a support material dispensing module including amaterial stretching mechanism configured to dispense and stretch asupport material across a cross section of the 3D hollow object wall;and wherein the support material dispensing module is constructed andarranged to dispense the support material separately prior to orconcurrently with the deposition of the portion of material forming atleast a layer of the 3D hollow object wall and at a location other thanthe location at which the 3D hollow object is being dispensed.
 2. Theapparatus according to claim 1, wherein the support material is alsodispensed at a location other than that at which the 3D hollow object isbeing dispensed.
 3. The apparatus according to claim 1, also comprisinga computer configured to generate a model and mark a planned contouroutline of a planned wall of the 3D object to be manufactured at across-section level at which the support material is to be positioned toprovide optimal structural strength and stability.
 4. The apparatusaccording to claim 3, wherein the support material dispensing moduledispenses the support material across a cross section contour of the 3Dobject including across a hollow or empty space inside the contour sothat to fit exactly the planned contour outline in accordance with agenerated model of the 3D object.
 5. The apparatus according to claim 3,wherein the support material dispensing module dispenses the supportmaterial across a cross section contour of the 3D object includingacross a hollow or empty space inside the contour so that to fitprecisely the planned contour outline in accordance with the generatedmodel of the 3D object and leave no appendages or excessive supportmaterial that later require trimming or removal at least at externalsurface of the object.
 6. The apparatus according to claim 3, whereinthe support material dispensing module dispenses support material alongthe contour outline or border in at least one of a semi-continuousfashion and in a form of deposited thickened drops so that to form edgeanchor bonding points to be integrated into a later dispensed wall of a3D object.
 7. The apparatus according to claim 1, wherein at least aportion of the support material is made of a single layer thickness. 8.The apparatus according to claim 1, wherein at least a portion of thesupport material has a thickness exceeding single layer thickness. 9.The apparatus according to claim 1, wherein the support material isdispensed in a form of a grid.
 10. The apparatus according to claim 1,wherein the support material is dispensed in a form of a grid alsoincluding ribs so that to provide additional strength as required. 11.The apparatus according to claim 1, wherein the 3D hollow objectmaterial deposition module is at least one of a group consisting of aninkjet module, extrusion module, and sintering module.
 12. The apparatusaccording to claim 1, wherein the 3D hollow object material solidifyingmodule solidifies the material by one of a group of radiationsconsisting of ultraviolet radiation, infrared radiation, microwaveradiation, and heat.
 13. The apparatus according to claim 1 wherein thesupport material dispensing module dispenses support material, which isat least one of a group of materials consisting of a metal grid, aplastic grid, a fabric grid, a grid made of material dissolvable in the3D hollow object material, and a combination of all of the above.
 14. Anapparatus for manufacturing of large shells, said apparatus comprising:a material deposition module configured to deposit a portion of materialforming at least a segment of a shell to be manufactured; a materialsolidifying module configured to solidify at least the portion ofmaterial deposited and forming at least a segment of the shell to bemanufactured; and a support material dispensing module including amaterial stretching mechanism configured to dispense and stretch asupport material across a cross section of the shell; and wherein thesupport material module dispenses the support material separately priorto or concurrently with the deposition of the portion of materialforming at least a layer of a 3D hollow object wall and at a locationother than that at which the 3D hollow object is being dispensed. 15.The apparatus according to claim 14, wherein the support materialdispensing module dispenses the support material across a cross sectioncontour of the 3D object including across a hollow or empty space insidethe contour so that to fit precisely a planned contour outline inaccordance with a generated model of the 3D object.
 16. An apparatus formanufacturing of large shells, said apparatus comprising: a materialdeposition module configured to deposit a portion of material forming atleast a segment of a shell to be manufactured; a material solidifyingmodule configured to solidify at least the portion of material depositedand forming at least a segment of the large shell to be manufactured;and a support material dispensing module including a material stretchingmechanism configured to dispense and stretch a support material across across section of the large shell; and wherein the support materialdispensing module is configured to dispense the support material acrossa cross section contour of a 3D object including across an empty spaceinside the contour so that to fit exactly a planned contour outline inaccordance with a generated model of a 3D object, wherein a size of the3D object is at least 500 mm×500 mm×500 mm.
 17. An apparatus formanufacturing of large shells having appendages, said apparatuscomprising: a material deposition module configured to deposit a portionof material forming at least a segment of a shell to be manufactured; amaterial solidifying module configured to solidify at least the portionof material deposited and forming at least a segment of the shell to bemanufactured; and a support material dispensing module configured todispense the support material across a cross section of the shell; andwherein the support material is in a form of members defining a gridhaving a first surface and at least one second surface and at least onerib having a thickness greater than that of the members defining thegrid; and wherein the material deposition module is configured todeposit material on the first surface forming at least a first portionof a shell to be manufactured and deposit material on the at least onesecond surface forming at least a second portion of a large shell to bemanufactured.
 18. The apparatus according to claim 17, wherein thesupport material dispensing module dispenses the support material acrossa cross section contour of the large shell including across a hollow orempty space inside the contour so that to fit exactly a planned contouroutline in accordance with a generated model of the large shell.
 19. Theapparatus according to claim 17, wherein the grid is flat and the firstsurface and second surface are on opposite sides of the grid.
 20. Theapparatus according to claim 17, wherein the support material or gridhas more than two surfaces laying in multiple planes in 3D space asrequired to provide optimal structural strength and stability to thelarge shells having appendages being manufactured.